The present invention relates to the determination of an analyte in a water sample. Such a method is described in DE 41 09 118 A1 where the cuvette has a one-dimensional barcode that contains information on the analyte to be determined. A cuvette is a vessel suitable for photometry which is transparent for the measuring radiation and into which the liquid sample is introduced and in which it is mixed with the reagent. The liquid analysis device comprises a rotation device with which the cuvette placed in the liquid analysis device can be rotated. The rotation device rotates the cuvette both while the barcode provided on the cuvette is read in the longitudinal direction and during photometry.
For an accurate quantitative determination of the analyte, the measuring signals acquired by the photometer must be converted into corresponding quantity measuring values using calibration data assigned to the respective analyte.